Tanshinone IIA attenuates hypoxic pulmonary hypertension via modulating KV currents

Unleashing the Potential of Nrf2: A Novel Therapeutic Target for Pulmonary Vascular Remodeling

Pulmonary vascular remodeling, characterized by the thickening of all three layers of the blood vessel wall, plays a central role in the pathogenesis of pulmonary hypertension (PH). Despite the approval of several drugs for PH treatment, their long-term therapeutic effect remains unsatisfactory, as they mainly focus on vasodilation rather than addressing vascular remodeling. Therefore, there is an urgent need for novel therapeutic targets in the treatment of PH. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a vital transcription factor that regulates endogenous antioxidant defense and emerges as a novel regulator of pulmonary vascular remodeling. Growing evidence has suggested an involvement of Nrf2 and its downstream transcriptional target in the process of pulmonary vascular remodeling. Pharmacologically targeting Nrf2 has demonstrated beneficial effects in various diseases, and several Nrf2 inducers are currently undergoing clinical trials. However, the exact potential and mechanism of Nrf2 as a therapeutic target in PH remain unknown. Thus, this review article aims to comprehensively explore the role and mechanism of Nrf2 in pulmonary vascular remodeling associated with PH. Additionally, we provide a summary of Nrf2 inducers that have shown therapeutic potential in addressing the underlying vascular remodeling processes in PH. Although Nrf2-related therapies hold great promise, further research is necessary before their clinical implementation can be fully realized.

Biomimetic Nanoparticle-Mediated Target Delivery of Hypoxia-Responsive Plasmid of Angiotensin-Converting Enzyme 2 to Reverse Hypoxic Pulmonary Hypertension

Hypoxic pulmonary hypertension (HPH) is characterized by pulmonary vascular sustained constriction and progressive remodeling, which are initiated by hypoxia then with hypoxia-induced additive factors including pulmonary vascular endothelium injury, intrapulmonary angiotension system imbalance, and inflammation. Now HPH is still an intractable disease lacking effective treatments. Gene therapy has a massive potential for HPH but is hindered by a lack of efficient targeted delivery and hypoxia-responsive regulation systems for transgenes. Herein, we constructed the hypoxia-responsive plasmid of angiotensin-converting enzyme 2 (ACE2) with endothelial-specific promoter Tie2 and a hypoxia response element and next prepared its biomimetic nanoparticle delivery system, named ACE2-CS-PRT@PM, by encapsulating the plasmid of ACE2 with protamine and chondroitin sulfate as the core then coated it with a platelet membrane as a shell for targeting the injured pulmonary vascular endothelium. ACE2-CS-PRT@PM has a 194.3 nm diameter with a platelet membrane-coating core-shell structure and a negatively charged surface, and it exhibits higher delivery efficiency targeting to pulmonary vascular endothelium and hypoxia-responsive overexpression of ACE2 in endothelial cells in a hypoxia environment. In vitro, ACE2-CS-PRT@PM significantly inhibited the hypoxia-induced proliferation of pulmonary smooth muscle cells. In vivo, ACE2-CS-PRT@PM potently ameliorated the hemodynamic dysfunction and morphological abnormality and largely reversed HPH via inhibiting the hypoxic proliferation of pulmonary artery smooth muscle cells, reducing pulmonary vascular remodeling, restoring balance to the intrapulmonary angiotension system, and improving the inflammatory microenvironment without any detectable toxicity. Therefore, ACE2-CS-PRT@PM is promising for the targeted gene therapy of HPH.

Natural Products for the Treatment of Pulmonary Hypertension: Mechanism, Progress, and Future Opportunities

Pulmonary hypertension (PH) is a lethal disease due to the remodeling of pulmonary vessels. Its pathophysiological characteristics include increased pulmonary arterial pressure and pulmonary vascular resistance, leading to right heart failure and death. The pathological mechanism of PH is complex and includes inflammation, oxidative stress, vasoconstriction/diastolic imbalance, genetic factors, and ion channel abnormalities. Currently, many clinical drugs for the treatment of PH mainly play their role by relaxing pulmonary arteries, and the treatment effect is limited. Recent studies have shown that various natural products have unique therapeutic advantages for PH with complex pathological mechanisms owing to their multitarget characteristics and low toxicity. This review summarizes the main natural products and their pharmacological mechanisms in PH treatment to provide a useful reference for future research and development of new anti-PH drugs and their mechanisms.

Traditional Chinese medicine monomers: Targeting pulmonary artery smooth muscle cells proliferation to treat pulmonary hypertension

Pulmonary hypertension (PH) is a complex multifactorial disease characterized by increased pulmonary vascular resistance and pulmonary vascular remodeling (PVR), with high morbidity, disability, and mortality. The abnormal proliferation of pulmonary artery smooth muscle cells (PASMCs) is the main pathological change causing PVR. At present, clinical treatment drugs for PH are limited, which can only improve symptoms and reduce hospitalization but cannot delay disease progression and reduce survival rate. In recent years, numerous studies have shown that traditional Chinese medicine monomers (TCMs) inhibit excessive proliferation of PASMCs resulting in alleviating PVR through multiple channels and multiple targets, which has attracted more and more attention in the treatment of PH. In this paper, the experimental evidence of inhibiting PASMCs proliferation by TCMs was summarized to provide some directions for the future development of these mentioned TCMs as anti-PH drugs in clinical.

Dan-Shen-Yin Granules Prevent Hypoxia-Induced Pulmonary Hypertension via STAT3/HIF-1α/VEGF and FAK/AKT Signaling Pathways

Traditional Chinese medicine (TCM) plays an important role in the treatment of complex diseases, especially cardiovascular diseases. However, it is hard to identify their modes of action on account of their multiple components. The present study aims to evaluate the effects of Dan-Shen-Yin (DSY) granules on hypoxia-induced pulmonary hypertension (HPH), and then to decipher the molecular mechanisms of DSY. Systematic pharmacology was employed to identify the targets of DSY on HPH. Furthermore, core genes were identified by constructing a protein-protein interaction (PPI) network and analyzed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes (KEGG) analysis. Related genes and pathways were verified using a hypoxia-induced mouse model and hypoxia-treated pulmonary artery cells. Based on network pharmacology, 147 potential targets of DSY on HPH were found, constructing a PPI network, and 13 hub genes were predicted. The results showed that the effect of DSY may be closely associated with AKT serine/threonine kinase 1 (AKT1), signal transducer and activator of transcription 3 (STAT3), and HIF-1 signaling pathways, as well as biological processes such as cell proliferation. Consistent with network pharmacology analysis, experiments in vivo demonstrated that DSY could prevent the development of HPH in a hypoxia-induced mouse model and alleviate pulmonary vascular remodeling. In addition, inhibition of STAT3/HIF-1α/VEGF and FAK/AKT signaling pathways might serve as mechanisms. Taken together, the network pharmacology analysis suggested that DSY exhibited therapeutic effects through multiple targets in the treatment of HPH. The inferences were initially confirmed by subsequent in vivo and in vitro studies. This study provides a novel perspective for studying the relevance of TCM and disease processes and illustrates the advantage of this approach and the multitargeted anti-HPH effect of DSY.

Eucommia ulmoides Oliver-Tribulus terrestris L. Drug Pair Regulates Ferroptosis by Mediating the Neurovascular-Related Ligand-Receptor Interaction Pathway- A Potential Drug Pair for Treatment Hypertension and Prevention Ischemic Stroke

Background

In this study, we used the network pharmacology approach to explore the potential disease targets of the Eucommia ulmoides Oliver (EUO)-Tribulus terrestris L. (TT) drug pair in the treatment of hypertension-associated neurovascular lesions and IS via the ferroptosis pathway.

Methods

We used the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform to search for the key active compounds and targets of the drug pair. Based on the GeneCards database, the relevant targets for the drug pair were obtained. Then, we performed the molecular docking of the screened core active ingredients and proteins using the DAVID database and the R AutoDock Vina software. Based on the GSE22255 dataset, these screened target proteins were used to build random forest (RF) and support vector machine (SVM) models. Finally, a new IS nomogram prediction model was constructed and evaluated.

Results

There were 36 active compounds in the EUO-TT drug pair. CHRM1, NR3C1, ADRB2, and OPRD1 proteins of the neuroactive ligand-receptor interaction pathway interacted with the proteins related to the ferroptosis pathway. Molecular docking experiments identified 12 active ingredients of the drug pair that may tightly bind to those target proteins. We constructed a visual IS nomogram prediction model using four genes (CHRM1, NR3C1, ADRB2, and OPRD1). The calibration curve, DCA, and clinical impact curves all indicated that the nomogram model is clinically applicable and diagnostically capable. CHRM1, NR3C1, ADRB2, and OPRD1, the target genes of the four effective components of the EUO-TT drug pair, were considered as risk markers for IS.

Conclusions

The active ingredients of EUO-TT drug pair may act on proteins associated with the neuroactive ligand-receptor interaction pathway to regulate ferroptosis in vascular neurons cells, ultimately affecting the onset and progression of hypertension.

Potential of natural products in the treatment of myocardial infarction: focus on molecular mechanisms

Although conventional drugs are widely used in the prevention and treatment of cardiovascular disease (CVD), they are being used less frequently due to concerns about possible side effects over the long term. There has been a renewed research interest in medicinal plant products, and their role in protecting the cardiovascular system and treating CVD, which are now being considered as potential alternatives to modern drugs. The most important mechanism causing damage to the myocardium after heart attack and reperfusion, is increased levels of free radicals and oxidative stress. Therefore, treatment approaches often focus on reducing free radicals or enhancing antioxidant defense mechanism. It has been previously reported that bioactive natural products can protect the heart muscle in myocardial infarction (MI). Since these compounds are readily available in fruits and vegetables, they could prevent the risk of MI if they are consumed daily. Although the benefits of a healthy diet are well known, many scientific studies have focused on whether pure natural compounds can prevent and treat MI. In this review we summarize the effects of curcumin, resveratrol, quercitin, berberine, and tanshinone on MI and CVD, and focus on their proposed molecular mechanisms of action.

Traditional Herbal Medicine Discovery for the Treatment and Prevention of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is characterized by pulmonary artery remodeling that may subsequently culminate in right heart failure and premature death. Although there are currently both non-pharmacological (lung transplantation, etc.) and pharmacological (Sildenafil, Bosentan, and new oral drugs on trial) therapies available, PAH remains a serious and fatal pulmonary disease. As a unique medical treatment, traditional herbal medicine (THM) treatment has gradually exerted its advantages in treating PAH worldwide through a multi-level and multi-target approach. Additionally, the potential mechanisms of THM were deciphered, including suppression of proliferation and apoptosis of pulmonary artery smooth muscle cells, controlling the processes of inflammation and oxidative stress, and regulating vasoconstriction and ion channels. In this review, the effects and mechanisms of the frequently studied compound THM, single herbal preparations, and multiple active components from THM are comprehensively summarized, as well as their related mechanisms on several classical preclinical PAH models. It is worth mentioning that sodium tanshinone IIA sulfonate sodium and tetramethylpyrazine are under clinical trials and are considered the most promoting medicines for PAH treatment. Last, reverse pharmacology, a strategy to discover THM or THM-derived components, has also been proposed here for PAH. This review discusses the current state of THM, their working mechanisms against PAH, and prospects of reverse pharmacology, which are expected to facilitate the natural anti-PAH medicine discovery and development and its bench-to-bedside transformation.

Natural ingredients from Chinese materia medica for pulmonary hypertension

Pulmonary hypertension (PH) is a severe pathophysiological condition characterized by pulmonary artery remodeling and continuous increases in pulmonary artery pressure, which may eventually develop to right heart failure and death. Although newly discovered and incredible treatment strategies in recent years have improved the prognosis of PH, limited types of effective and economical drugs for PH still makes it as a life-threatening disease. Some drugs from Chinese materia medica (CMM) have been traditionally applied in the treatment of lung diseases. Accumulating evidence suggests active pharmaceutical ingredients (APIs) derived from those medicines brings promising future for the prevention and treatment of PH. In this review, we summarized the pharmacological effects of APIs derived from CMM which are potent in treating PH, so as to provide new thoughts for initial drug discovery and identification of potential therapeutic strategies in alternative medicine for PH.

Tanshinones and their Derivatives: Heterocyclic Ring-Fused Diterpenes of Biological Interest

The available scientific literature regarding tanshinones is very abundant, and after its review, it is noticeable that most of the articles focus on the properties of tanshinone I, cryptotanshinone, tanshinone IIA, sodium tanshinone IIA sulfonate and the dried root extract of Salvia miltiorrhiza (Tan- Shen). However, although these products have demonstrated important biological properties in both in vitro and in vivo models, their poor solubility and bioavailability have limited their clinical applications. For these reasons, many studies have focused on the search for new pharmaceutical formulations for tanshinones, as well as the synthesis of new derivatives that improve their biological properties. To provide new insights into the critical path ahead, we systemically reviewed the most recent advances (reported since 2015) on tanshinones in scientific databases (PubMed, Web of Science, Medline, Scopus, and Clinical Trials). With a broader perspective, we offer an update on the last five years of new research on these quinones, focusing on their synthesis, biological activity on noncommunicable diseases and drug delivery systems, to support future research on its clinical applications.

The protective effect of tanshinone IIa on endothelial cells: a generalist among clinical therapeutics

INTRODUCTION

Tanshinone IIa (TSA) has been approved to treat cardiovascular diseases by the China State Food and Drug Administration. TSA has exhibited a variety of pharmacological effects, including vasodilator, antioxidant, anti-inflammatory, and anti-tumor properties. Endothelial cells play an important physiological role in vascular homeostasis and control inflammation, coagulation, and thrombosis. Accumulating studies have shown that TSA can improve endothelial function through various pathways.

AREAS COVERED

The PubMed database was reviewed for relevant papers published up to 2020. This review summarizes the current clinical and pharmaceutical studies to provide a systemic overview of the pharmacological and therapeutic effects of TSA on endothelial cells.

EXPERT OPINION

TSA is a representative monomeric compound extracted from Danshen and it exhibits significant pharmacological and therapeutic properties to improve endothelial cell function, including alleviating oxidative stress, attenuating inflammatory injury, modulating ion channels and so on. TSA represents a spectrum of agents that are extracted from plants and can restore the endothelial function to establish the beneficial and harmless molecular therapeutics. This also suggests the possible detection of endothelial cells for very early diagnosis of diseases. In future, precise therapeutic methods will be developed to repair endothelial cells injury and recover endothelial dysfunction.

Vasoconstrictor Mechanisms in Chronic Hypoxia-Induced Pulmonary Hypertension: Role of Oxidant Signaling

Elevated resistance of pulmonary circulation after chronic hypoxia exposure leads to pulmonary hypertension. Contributing to this pathological process is enhanced pulmonary vasoconstriction through both calcium-dependent and calcium sensitization mechanisms. Reactive oxygen species (ROS), as a result of increased enzymatic production and/or decreased scavenging, participate in augmentation of pulmonary arterial constriction by potentiating calcium influx as well as activation of myofilament sensitization, therefore mediating the development of pulmonary hypertension. Here, we review the effects of chronic hypoxia on sources of ROS within the pulmonary vasculature including NADPH oxidases, mitochondria, uncoupled endothelial nitric oxide synthase, xanthine oxidase, monoamine oxidases and dysfunctional superoxide dismutases. We also summarize the ROS-induced functional alterations of various Ca2+ and K+ channels involved in regulating Ca2+ influx, and of Rho kinase that is responsible for myofilament Ca2+ sensitivity. A variety of antioxidants have been shown to have beneficial therapeutic effects in animal models of pulmonary hypertension, supporting the role of ROS in the development of pulmonary hypertension. A better understanding of the mechanisms by which ROS enhance vasoconstriction will be useful in evaluating the efficacy of antioxidants for the treatment of pulmonary hypertension.

A network pharmacology approach to investigating the mechanism of Tanshinone IIA for the treatment of liver fibrosis

ETHNOPHARMACOLOGICAL REVELVANCE

Tanshinone IIA (TIIA) is a major component extracted from the traditional herbal medicine salvia miltiorrhiza (Danshen), which activates blood circulation and treats chronic hepatitis and liver fibrosis. However, the underlying molecular mechanism of TIIA against hepatic fibrosis is still largely unknown.

AIM OF THE STUDY

The present study aimed to evaluate the antifibrotic effects of TIIA in liver fibrosis and investigate its underlying mechanism through network pharmacology-based prediction and experimental verification.

MATERIALS AND METHODS

In this study, a "TIIA-targets-liver fibrosis" network was constructed by combining the TIIA-specific and hepatic fibrosis-specific targets with protein-protein interactions (PPIS), and network pharmacology was applied to identify the potential targets and mechanisms of TIIA in the treatment of hepatic fibrosis. The antifibrotic effect of TIIA was investigated in CCl4-induced liver fibrosis in rats in vivo and in the human HSC line LX2 in vitro.

RESULTS

We identified 75 potential targets of TIIA and 1382 targets of liver fibrosis. Subsequently, the 29 target proteins that overlapped between the potential TIIA targets and the liver fibrosis targets indicated that TIIA has potential antifibrotic effects through regulating multiple targets, including c-Jun, c-Myc, CCND1, MMP9 and P65. Pathway and functional enrichment analysis of these putative targets showed that TIIA could regulate the MAPK, PI3K/Akt and Wnt signaling pathways. Consistently, in vivo and in vitro experiments indicated that TIIA attenuated CCl4-induced liver injury and fibrosis and inhibited hepatic stellate cell (HSC) proliferation and activation; these findings were concomitant with the decreased expression of α-smooth muscle actin (α-SMA) and human α2 (I) collagen (COL1A2). Moreover, TIIA remarkably downregulated the expression of c-Jun, c-Myc, MMP9, PI3K and P38 proteins, which were upregulated in CCl4-induced hepatic fibrosis in vivo. TIIA significantly downregulated the expression of c-Jun, p-c-Jun, c-Myc, CCND1, MMP9, P65, P-P65, PI3K and P38 proteins, which were upregulated during HSC activation in vitro.

CONCLUSION

Our study demonstrated that TIIA could significantly improve liver function, decrease liver injury, alleviate ECM accumulation, and attenuate HSC proliferation and activation, thus exerting an antifibrotic effect. The possible molecular mechanism involved MAPK, Wnt and PI3K/Akt signaling pathways via inhibiting c-Jun, p-c-Jun, c-Myc, CCND1, MMP9, P65, P-P65, PI3K and P38. Overall, our results suggest that TIIA could alleviate liver fibrosis through multiple targets and multiple signaling pathways and provide deep insight into the pharmacological mechanisms of TIIA in the treatment of hepatic fibrosis.

Tanshinone IIA pretreatment promotes cell survival in human lung epithelial cells under hypoxia via AP-1-Nrf2 transcription factor

Activator protein-1 (AP-1) plays a decisive role in cell proliferation, apoptosis, and inflammation under hypoxia; thus, AP-1 subunits or dimers could be modulated for a desired phenomenon in a cell using a suitable compound of therapeutic potential. Herein, we used Tanshinone-IIA as an AP-1 (subunits) modulator, and the purpose of the study was to investigate the signaling mechanism exhibited by Tan-IIA in facilitating tolerance to hypoxia. A549 cells were pretreated with Tan-IIA and exposed to hypoxia for 6, 12, 24, and 48 h. Biochemical and molecular parameters were assessed in order to trace the signaling pathway. Tan-IIA attenuated hypoxia-induced oxidative stress by modulating the expression of AP-1 subunits (via. MAPK) and Nrf2 transcription factor, which in turn were responsible for maintaining the higher levels of antioxidant enzymes and genes (HO). Tan-IIA increased the cell survival. This could be attributed to an increased NO level via iNOS gene and activated JNK, ERK pathway that induced c-jun/c-fos, c-jun/fosB, junD/c-fos, and junD/fosB heterodimers. This in turn leads to the cell cycle progression by activating cyclins (D and B). This was further confirmed by the lower levels of p53 and their downstream genes (p16, p21, p27). In addition, Tan-IIA decreased pro-inflammatory cytokine levels by inhibiting the formation of junB/fra-1 heterodimer regulated by p38. Tan-IIA increased cell survival to hypoxia by maintaining the higher levels of cellular iNOS, HO-1, jun-D, c-jun, fos B via Nrf2-AP-1.

Natural plant products in treatment of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a severe disease characterized by progressive remodeling of distal pulmonary arteries and persistent elevation of pulmonary vascular resistance (PVR), which leads to right ventricular dysfunction, heart failure, and eventually death. Although treatment responsiveness for this disease is improving, it continues to be a life-threatening condition. With the clinical efficacy of natural plant products being fully confirmed by years of practice, more and more recognition and attention have been obtained from the international pharmaceutical industry. Moreover, studies over the past decades have demonstrated that drugs derived from natural plants show unique advantages and broad application prospects in PAH treatment, not to mention the historical application of Chinese traditional medicine in cardiopulmonary diseases. In this review, we focus on summarizing natural plant compounds with therapeutic properties in PAH, according to the extracts, fractions, and pure compounds from plants into categories, hoping it to be helpful for basic research and clinical application.

Salvia miltiorrhiza: A Potential Red Light to the Development of Cardiovascular Diseases

Salvia miltiorrhiza Bunge, also known as Danshen in Chinese, has been widely used to treat cardiovascular diseases (CVD) in China and other Asia countries. Here, we summarize literatures of the historical traditional Chinese medicine (TCM) interpretation of the action of Salvia miltiorrhiza, its use in current clinical trials, its main phytochemical constituents and its pharmacological findings by consulting Pubmed, China Knowledge Resource Integrated, China Science and Technology Journal, and the Web of Science Databases. Since 2000, 39 clinical trials have been identified that used S. miltiorrhiza in TCM prescriptions alone or with other herbs for the treatment of patients with CVD. More than 200 individual compounds have been isolated and characterized from S. miltiorrhiza, which exhibited various pharmacological activities targeting different pathways for the treatment of CVD in various animal and cell models. The isolated compounds may provide new perspectives in alternative treatment regimes and reveal novel chemical scaffolds for the development of anti-CVD drugs. Meanwhile, there are also some rising concerns of the potential side effects and drug-drug interactions of this plant. The insights gained from this study will help us to better understanding of the actions of this herb for management of cardiovascular disorders. As an herb of red root, S. miltiorrhiza will act as a potential red light to prevent the development of CVD.

Sodium tanshinone IIA sulfonate stimulated Cl- secretion in mouse trachea

Sodium tanshinone IIA sulfonate (STS) is a derivate of tanshinone IIA, a lipophilic compound in Salvia miltiorrhiza. This study aimed to investigate the effect of STS on ion transport in mouse tracheal epithelium and the mechanisms underlying it. Short-circuit current (I_sc) was measured to evaluate the effect of STS on transepithelial ion transport. Intracellular Ca²⁺ imaging was performed to observe intracellular Ca²⁺ concentration ([Ca²⁺]_i) changes induced by STS in primary cultured mouse tracheal epithelial cells. Results showed that the apical application of STS at mouse trachea elicited an increase of I_sc, which was abrogated by atropine, an antagonist of muscarinic acetylcholine receptor (mAChR). By removing ambient Cl⁻ or applying blockers of Ca²⁺-activated Cl⁻ channel (CaCC), the response of STS-induced I_sc was suppressed. Moreover, STS elevated the [Ca²⁺]_i in mouse tracheal epithelial cells. As a result, STS stimulated Cl⁻ secretion in mouse tracheal epithelium via CaCC in an mAChR-dependent way. Due to the critical role of Cl⁻ secretion in airway hydration, our findings suggested that STS may be used to ameliorate the airway dehydration symptom in cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD).

Recent insights into the biological activities and drug delivery systems of tanshinones

Tanshinones, the major lipid-soluble pharmacological constituents of the Chinese medicinal herb Tanshen (Salvia miltiorrhiza), have attracted growing scientific attention because of the prospective biomedical applications of these compounds. Numerous pharmacological activities, including anti-inflammatory, anticancer, and cardio-cerebrovascular protection activities, are exhibited by the three primary bioactive constituents among the tanshinones, ie, tanshinone I (TNI), tanshinone IIA (TNIIA), and cryptotanshinone (CPT). However, due to their poor solubility and low dissolution rate, the clinical applications of TNI, TNIIA, and CPT are limited. To solve these problems, many studies have focused on loading tanshinones into liposomes, nanoparticles, microemulsions, cyclodextrin inclusions, solid dispersions, and so on. In this review, we aim to offer an updated summary of the biological activities and drug delivery systems of tanshinones to provide a reference for these constituents in clinical applications.